Common Lisp implementations for Unix have traditionally provided a rich development environment at the expense of an inefficient delivery environment. The goal of WCL is to allow hundreds of Lisp applications to be realistically available at once, while allowing many of them to run concurrently. WCL accomplishes this by providing Common Lisp as a Unix shared library that can be linked with Lisp and C code to produce efficient applications. For example, the executable for a Lisp version of the canonical "Hello World!" program requires only 20k bytes.